md: support blocking writes to an array on device failure

Allows a userspace metadata handler to take action upon detecting a device
failure.

Based on an original patch by Neil Brown.

Changes:
-added blocked_wait waitqueue to rdev
-don't qualify Blocked with Faulty always let userspace block writes
-added md_wait_for_blocked_rdev to wait for the block device to be clear, if
 userspace misses the notification another one is sent every 5 seconds
-set MD_RECOVERY_NEEDED after clearing "blocked"
-kill DoBlock flag, just test mddev->external

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 115 insertions, 7 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index bec00b201a73..83eb78b00137 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1828,6 +1828,10 @@ state_show(mdk_rdev_t *rdev, char *page)
                 len += sprintf(page+len, "%swrite_mostly",sep);
                 sep = ",";
         }
+        if (test_bit(Blocked, &rdev->flags)) {
+                len += sprintf(page+len, "%sblocked", sep);
+                sep = ",";
+        }
         if (!test_bit(Faulty, &rdev->flags) &&
             !test_bit(In_sync, &rdev->flags)) {
                 len += sprintf(page+len, "%sspare", sep);
@@ -1844,6 +1848,8 @@ state_store(mdk_rdev_t *rdev, const char *buf, size_t len)
          *  remove  - disconnects the device
          *  writemostly - sets write_mostly
          *  -writemostly - clears write_mostly
+         *  blocked - sets the Blocked flag
+         *  -blocked - clears the Blocked flag
          */
         int err = -EINVAL;
         if (cmd_match(buf, "faulty") && rdev->mddev->pers) {
@@ -1866,6 +1872,16 @@ state_store(mdk_rdev_t *rdev, const char *buf, size_t len)
         } else if (cmd_match(buf, "-writemostly")) {
                 clear_bit(WriteMostly, &rdev->flags);
                 err = 0;
+        } else if (cmd_match(buf, "blocked")) {
+                set_bit(Blocked, &rdev->flags);
+                err = 0;
+        } else if (cmd_match(buf, "-blocked")) {
+                clear_bit(Blocked, &rdev->flags);
+                wake_up(&rdev->blocked_wait);
+                set_bit(MD_RECOVERY_NEEDED, &rdev->mddev->recovery);
+                md_wakeup_thread(rdev->mddev->thread);
+
+                err = 0;
         }
         return err ? err : len;
 }
@@ -2194,7 +2210,9 @@ static mdk_rdev_t *md_import_device(dev_t newdev, int super_format, int super_mi
                         goto abort_free;
                 }
         }
+
         INIT_LIST_HEAD(&rdev->same_set);
+        init_waitqueue_head(&rdev->blocked_wait);
 
         return rdev;
 
@@ -4958,6 +4976,9 @@ void md_error(mddev_t *mddev, mdk_rdev_t *rdev)
 
         if (!rdev || test_bit(Faulty, &rdev->flags))
                 return;
+
+        if (mddev->external)
+                set_bit(Blocked, &rdev->flags);
 /*
         dprintk("md_error dev:%s, rdev:(%d:%d), (caller: %p,%p,%p,%p).\n",
                 mdname(mddev),
@@ -5760,7 +5781,7 @@ static int remove_and_add_spares(mddev_t *mddev)
 
         rdev_for_each(rdev, rtmp, mddev)
                 if (rdev->raid_disk >= 0 &&
-                    !mddev->external &&
+                    !test_bit(Blocked, &rdev->flags) &&
                     (test_bit(Faulty, &rdev->flags) ||
                      ! test_bit(In_sync, &rdev->flags)) &&
                     atomic_read(&rdev->nr_pending)==0) {
@@ -5959,6 +5980,16 @@ void md_check_recovery(mddev_t *mddev)
         }
 }
 
+void md_wait_for_blocked_rdev(mdk_rdev_t *rdev, mddev_t *mddev)
+{
+        sysfs_notify(&rdev->kobj, NULL, "state");
+        wait_event_timeout(rdev->blocked_wait,
+                           !test_bit(Blocked, &rdev->flags),
+                           msecs_to_jiffies(5000));
+        rdev_dec_pending(rdev, mddev);
+}
+EXPORT_SYMBOL(md_wait_for_blocked_rdev);
+
 static int md_notify_reboot(struct notifier_block *this,
                             unsigned long code, void *x)
 {
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 9fd473a6dbf5..6778b7cb39bd 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -773,7 +773,6 @@ static int make_request(struct request_queue *q, struct bio * bio)
         r1bio_t *r1_bio;
         struct bio *read_bio;
         int i, targets = 0, disks;
-        mdk_rdev_t *rdev;
         struct bitmap *bitmap = mddev->bitmap;
         unsigned long flags;
         struct bio_list bl;
@@ -781,6 +780,7 @@ static int make_request(struct request_queue *q, struct bio * bio)
         const int rw = bio_data_dir(bio);
         const int do_sync = bio_sync(bio);
         int do_barriers;
+        mdk_rdev_t *blocked_rdev;
 
         /*
          * Register the new request and wait if the reconstruction
@@ -862,10 +862,17 @@ static int make_request(struct request_queue *q, struct bio * bio)
         first = 0;
         }
 #endif
+ retry_write:
+        blocked_rdev = NULL;
         rcu_read_lock();
         for (i = 0;  i < disks; i++) {
-                if ((rdev=rcu_dereference(conf->mirrors[i].rdev)) != NULL &&
-                    !test_bit(Faulty, &rdev->flags)) {
+                mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[i].rdev);
+                if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
+                        atomic_inc(&rdev->nr_pending);
+                        blocked_rdev = rdev;
+                        break;
+                }
+                if (rdev && !test_bit(Faulty, &rdev->flags)) {
                         atomic_inc(&rdev->nr_pending);
                         if (test_bit(Faulty, &rdev->flags)) {
                                 rdev_dec_pending(rdev, mddev);
@@ -878,6 +885,20 @@ static int make_request(struct request_queue *q, struct bio * bio)
         }
         rcu_read_unlock();
 
+        if (unlikely(blocked_rdev)) {
+                /* Wait for this device to become unblocked */
+                int j;
+
+                for (j = 0; j < i; j++)
+                        if (r1_bio->bios[j])
+                                rdev_dec_pending(conf->mirrors[j].rdev, mddev);
+
+                allow_barrier(conf);
+                md_wait_for_blocked_rdev(blocked_rdev, mddev);
+                wait_barrier(conf);
+                goto retry_write;
+        }
+
         BUG_ON(targets == 0); /* we never fail the last device */
 
         if (targets < conf->raid_disks) {
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 1e96aa3ff513..5938fa962922 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -790,6 +790,7 @@ static int make_request(struct request_queue *q, struct bio * bio)
         const int do_sync = bio_sync(bio);
         struct bio_list bl;
         unsigned long flags;
+        mdk_rdev_t *blocked_rdev;
 
         if (unlikely(bio_barrier(bio))) {
                 bio_endio(bio, -EOPNOTSUPP);
@@ -879,17 +880,23 @@ static int make_request(struct request_queue *q, struct bio * bio)
         /*
          * WRITE:
          */
-        /* first select target devices under spinlock and
+        /* first select target devices under rcu_lock and
          * inc refcount on their rdev.  Record them by setting
          * bios[x] to bio
          */
         raid10_find_phys(conf, r10_bio);
+ retry_write:
+        blocked_rdev = 0;
         rcu_read_lock();
         for (i = 0;  i < conf->copies; i++) {
                 int d = r10_bio->devs[i].devnum;
                 mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[d].rdev);
-                if (rdev &&
-                    !test_bit(Faulty, &rdev->flags)) {
+                if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
+                        atomic_inc(&rdev->nr_pending);
+                        blocked_rdev = rdev;
+                        break;
+                }
+                if (rdev && !test_bit(Faulty, &rdev->flags)) {
                         atomic_inc(&rdev->nr_pending);
                         r10_bio->devs[i].bio = bio;
                 } else {
@@ -899,6 +906,22 @@ static int make_request(struct request_queue *q, struct bio * bio)
         }
         rcu_read_unlock();
 
+        if (unlikely(blocked_rdev)) {
+                /* Have to wait for this device to get unblocked, then retry */
+                int j;
+                int d;
+
+                for (j = 0; j < i; j++)
+                        if (r10_bio->devs[j].bio) {
+                                d = r10_bio->devs[j].devnum;
+                                rdev_dec_pending(conf->mirrors[d].rdev, mddev);
+                        }
+                allow_barrier(conf);
+                md_wait_for_blocked_rdev(blocked_rdev, mddev);
+                wait_barrier(conf);
+                goto retry_write;
+        }
+
         atomic_set(&r10_bio->remaining, 0);
 
         bio_list_init(&bl);
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 968dacaced6d..087eee0cb809 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2607,6 +2607,7 @@ static void handle_stripe_expansion(raid5_conf_t *conf, struct stripe_head *sh,
         }
 }
 
+
 /*
  * handle_stripe - do things to a stripe.
  *
@@ -2632,6 +2633,7 @@ static void handle_stripe5(struct stripe_head *sh)
         struct stripe_head_state s;
         struct r5dev *dev;
         unsigned long pending = 0;
+        mdk_rdev_t *blocked_rdev = NULL;
 
         memset(&s, 0, sizeof(s));
         pr_debug("handling stripe %llu, state=%#lx cnt=%d, pd_idx=%d "
@@ -2691,6 +2693,11 @@ static void handle_stripe5(struct stripe_head *sh)
                 if (dev->written)
                         s.written++;
                 rdev = rcu_dereference(conf->disks[i].rdev);
+                if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
+                        blocked_rdev = rdev;
+                        atomic_inc(&rdev->nr_pending);
+                        break;
+                }
                 if (!rdev || !test_bit(In_sync, &rdev->flags)) {
                         /* The ReadError flag will just be confusing now */
                         clear_bit(R5_ReadError, &dev->flags);
@@ -2705,6 +2712,11 @@ static void handle_stripe5(struct stripe_head *sh)
         }
         rcu_read_unlock();
 
+        if (unlikely(blocked_rdev)) {
+                set_bit(STRIPE_HANDLE, &sh->state);
+                goto unlock;
+        }
+
         if (s.to_fill && !test_and_set_bit(STRIPE_OP_BIOFILL, &sh->ops.pending))
                 sh->ops.count++;
 
@@ -2894,8 +2906,13 @@ static void handle_stripe5(struct stripe_head *sh)
         if (sh->ops.count)
                 pending = get_stripe_work(sh);
 
+ unlock:
         spin_unlock(&sh->lock);
 
+        /* wait for this device to become unblocked */
+        if (unlikely(blocked_rdev))
+                md_wait_for_blocked_rdev(blocked_rdev, conf->mddev);
+
         if (pending)
                 raid5_run_ops(sh, pending);
 
@@ -2912,6 +2929,7 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
         struct stripe_head_state s;
         struct r6_state r6s;
         struct r5dev *dev, *pdev, *qdev;
+        mdk_rdev_t *blocked_rdev = NULL;
 
         r6s.qd_idx = raid6_next_disk(pd_idx, disks);
         pr_debug("handling stripe %llu, state=%#lx cnt=%d, "
@@ -2975,6 +2993,11 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
                 if (dev->written)
                         s.written++;
                 rdev = rcu_dereference(conf->disks[i].rdev);
+                if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
+                        blocked_rdev = rdev;
+                        atomic_inc(&rdev->nr_pending);
+                        break;
+                }
                 if (!rdev || !test_bit(In_sync, &rdev->flags)) {
                         /* The ReadError flag will just be confusing now */
                         clear_bit(R5_ReadError, &dev->flags);
@@ -2989,6 +3012,11 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
                         set_bit(R5_Insync, &dev->flags);
         }
         rcu_read_unlock();
+
+        if (unlikely(blocked_rdev)) {
+                set_bit(STRIPE_HANDLE, &sh->state);
+                goto unlock;
+        }
         pr_debug("locked=%d uptodate=%d to_read=%d"
                " to_write=%d failed=%d failed_num=%d,%d\n",
                s.locked, s.uptodate, s.to_read, s.to_write, s.failed,
@@ -3094,8 +3122,13 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
             !test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending))
                 handle_stripe_expansion(conf, sh, &r6s);
 
+ unlock:
         spin_unlock(&sh->lock);
 
+        /* wait for this device to become unblocked */
+        if (unlikely(blocked_rdev))
+                md_wait_for_blocked_rdev(blocked_rdev, conf->mddev);
+
         return_io(return_bi);
 
         for (i=disks; i-- ;) {